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                                                                   Exhibit 10.27

                              MKS INSTRUMENTS, INC.

                   INTERNATIONAL EMPLOYEE STOCK PURCHASE PLAN

     The purpose of this Plan is to provide eligible employees of certain
non-U.S. subsidiaries of MKS Instruments, Inc. (the "Company") with
opportunities to purchase shares of the Company's common stock (the "Common
Stock"), commencing on March 1, 2000. Fifty thousand (50,000) shares of Common
Stock in the aggregate have been approved for this purpose.

     1.   ADMINISTRATION. The Plan will be administered by the Company's Board
of Directors (the "Board") or by a Committee appointed by the Board (the
"Committee"). The Board or the Committee has authority to make rules and
regulations for the administration of the Plan and its interpretation and
decisions with regard thereto shall be final and conclusive.

     2.   ELIGIBILITY. All employees of any non-U.S. subsidiary of the Company
designated by the Board or the Committee from time to time (a "Subsidiary"),
excluding Officers and Directors of the Company who are employees of a
Subsidiary, are eligible to participate in any one or more of the offerings of
Options (as defined in Section 9) to purchase Common Stock under the Plan
provided that:

          a. they have been employed by the Subsidiary for at least six (6)
     months prior to enrolling in the Plan;

          b. they are employees of the Subsidiary on the first day of the
     applicable Plan Period (as defined below);

          c. to the extent local law permits such a requirement, they are
     customarily employed by a Subsidiary for more than twenty (20) hours a week
     and for more than five (5) months in a calendar year; and

          d. they meet any other requirements imposed from time to time by the
     Board or the Committee on employees of one or more subsidiaries.

     No employee may be granted an option hereunder if such employee,
immediately after the option is granted, owns 5% or more of the total combined
voting power or value of the stock of the Company or any subsidiary. For
purposes of the preceding sentence, the attribution rules of Section 424(d) of
the U.S. Internal Revenue Code of 1986, as amended (the "Code") shall apply in
determining the stock ownership of an employee, and all stock which the employee
has a contractual right to purchase shall be treated as stock owned by the
employee.

     3.   OFFERINGS. The Company will make one or more offerings ("Offerings")
to employees to purchase stock under this Plan. The first Offering will begin on
March 1, 2000 or the first business day thereafter (the "Offering Commencement
Dates") and end

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on May 31, 2000. Thereafter, each June 1 and December 1 or the first business
day thereafter will be an Offering Commencement Date. Each Offering Commencement
Date after March 1, 2000 will begin a six (6) month period (a "Plan Period")
during which payroll deductions will be made and held for the purchase of Common
Stock at the end of the Plan Period. The Board or the Committee may, at its
discretion, choose a different Plan Period of twelve (12) months or less for
subsequent Offerings.

     4.   PARTICIPATION.

     a.   ENROLLMENT. An employee eligible on the Offering Commencement Date of
any Offering may participate in such Offering by enrolling, in such manner and
at such time approved, from time to time, by the Board or the Committee, prior
to the applicable Offering Commencement Date in said Offering. The enrollment
will authorize a regular payroll deduction from the Compensation received by the
employee during the Plan Period. Unless an employee changes his enrollment in a
manner prescribed by the Committee from time to time or withdraws from the Plan,
his deductions and purchases will continue at the same rate for future Offerings
under the Plan as long as the Plan remains in effect. The term "Compensation"
shall be defined by the Board or the Committee from time to time, but until
modified shall mean regular base salary, including overtime, shift premium,
incentive or bonus awards and sales commissions and excluding allowances and
reimbursements for expenses such as relocation allowances for travel expenses,
income or gains on the exercise of Company stock options or stock appreciation
rights, and similar items whether or not taxable.

     b.   TAX WITHHOLDING AUTHORIZED. The enrollment of each employee shall
constitute such participating employee's authorization of his or her employer to
deduct from such employee's compensation in the relevant month or months (or
subsequent months, if appropriate) any amount necessary for the payment or
reimbursement of any tax liability payable by such employee with respect to the
grant or exercise of the options hereunder, or the sale of any stock acquired
through the exercise of such option.

     5.   DEDUCTIONS. The Company will maintain payroll deduction accounts for
all participating employees. With respect to any Offering made under this Plan,
an employee may authorize a payroll deduction in any whole percent amount
between one and ten percent (1-10%) of the Compensation he or she receives
during the Plan Period or such shorter period during which deductions from
payroll are made (or such other percentages as may be established by the Board
or the Committee). Any change in Compensation during the Plan Period will result
in an automatic corresponding change in the amount withheld. The payroll
deductions shall be made in the applicable local currency and will be converted
into United States currency at the prevailing rate of exchange in effect on such
date as the Board or Committee shall determine. All amounts deducted may be
transferred to an account of the Company or the Subsidiary outside the country
in which such employee is employed.

     No employee may be granted an Option (as defined in Section 9) which
permits his rights to purchase Common Stock under this Plan and any other
employee stock purchase plan (as defined by the Committee or Board) of the
Company and its

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subsidiaries, to accrue at a rate which exceeds $25,000 of the fair market value
of such Common Stock (determined at the Offering Commencement Date of the Plan
Period) for each calendar year in which the Option is outstanding at any time.

     6.   DEDUCTION CHANGES. An employee may decrease, subject to Section 5
hereof, or discontinue his payroll deduction once during any Plan Period, up to
such date prior to the close of business on the last business day, and in such
manner as is permitted by the Board or Committee. However, an employee may not
elect to increase his payroll deduction during a Plan Period. If an employee
elects to discontinue his payroll deductions during a Plan Period but does not
elect to withdraw his funds pursuant to Section 8 hereof, amounts previously
withheld will be applied to the purchase of Common Stock on the Exercise Date
(as defined below).

     7.   INTEREST. Interest will not be paid on any employee accounts.

     8.   WITHDRAWAL OF FUNDS. An employee may at any time up to a deadline
established by the Committee or the Board, prior to the close of business on the
last business day in a Plan Period, and for any reason, permanently draw out the
balance accumulated in the employee's account, which will be paid in the local
currency or, in Euros, at the discretion of the Board or the Committee if such
employee is employed in a country which maintains a fixed exchange rate between
its local currency and the Euro ("Repayment in Euros"), and thereby withdraw
from participation in an Offering. Partial withdrawals are not permitted. The
employee may not begin participation again during the remainder of the Plan
Period. The employee may participate in any subsequent Offering in accordance
with terms and conditions established by the Board or the Committee.

     9.   PURCHASE OF SHARES. On the Offering Commencement Date of each Plan
Period, the Company will grant to each eligible employee who is then a
participant in the Plan an option ("Option") to purchase on the last business
day of such Plan Period (the "Exercise Date"), at the Option Price hereinafter
provided for, the largest number of shares (including fractional shares) of
Common Stock of the Company as does not exceed the number of shares determined
by multiplying $2,083 by the number of full months in the Offering Period and
dividing the results by the closing price (as defined below) on the Offering
Commencement Date of such Plan Period.

     The purchase price for each share purchased will be 85% of the Fair Market
Value of the Common Stock on (i) the first business day of such Plan Period or
(ii) the Exercise Date, whichever Fair Market Value shall be less. Such Fair
Market Value shall be (a) the closing price on any national securities exchange
on which the Common Stock is listed, (b) the closing price of the Common Stock
on the Nasdaq National Market or (c) the average of the closing bid price and
asked price in the over-the-counter-market, whichever is applicable, as
published in THE WALL STREET JOURNAL. If no sales of Common Stock were made on
such a day, the price of the Common Stock for purposes of clauses (a) and (b)
above shall be based on the reported price for the next preceding day on which
sales were made.

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     Each employee who continues to be a participant in the Plan on the Exercise
Date shall be deemed to have exercised his Option at the Option Price on such
date and shall be deemed to have purchased from the Company the number of shares
of Common Stock (including fractional shares) reserved for the purpose of the
Plan that his accumulated payroll deductions on such date will pay for, in
United States currency as of that date, but not in excess of the maximum number
determined in the manner set forth above. The Board or the Committee may, in its
discretion, limit the purchase to only whole shares and not fractional shares.

     Any balance remaining in an employee's payroll deduction account at the end
of a Plan Period will be automatically refunded to the employee in the local
currency or at the discretion of the Committee or the Board there may be
Repayment in Euros, except that any balance which is less than the purchase
price of one share of Common Stock will be carried forward into the employee's
payroll deduction account for the following Offering, unless the employee elects
not to participate in the following Offering under the Plan, in which case the
balance shall be refunded.

     10.  ISSUANCE OF CERTIFICATES. Certificates representing shares of Common
Stock purchased under the Plan may be issued only in the name of the employee,
in the name of the employee and another person of legal age as joint tenants
with rights of survivorship, or (in the Company's sole discretion) in the name
of a brokerage firm, bank or other nominee holder designated by the employee.
The Company may, in its sole discretion and in compliance with applicable laws,
authorize the use of book entry registration of shares in lieu of issuing stock
certificates.

     11.  RIGHTS ON RETIREMENT DEATH OR TERMINATION OF EMPLOYMENT. In the event
of a participating employee's termination of employment prior to the last
business day of a Plan Period, no payroll deduction shall be taken from any pay
due and owing to an employee and the balance in the employee's account shall be
paid to the employee or, in the event of the employee's death, and subject to
the terms of applicable law, (a) to a beneficiary previously designated in a
revocable notice signed by the employee (with any spousal consent required under
local law) or (b) in the absence of such a designated beneficiary, to the
personal representative of the employee's estate or (c) if no such personal
representative has been appointed to the knowledge of the Company, to such other
person(s) as the Company may, in its discretion, designate. If, prior to the
last business day of the Plan Period, the designated Subsidiary by which an
employee is employed shall cease to be a subsidiary of the Company, or if the
employee is transferred to a subsidiary of the Company that is not a Subsidiary
under the Plan, the employee shall be deemed to have terminated employment for
the purposes of this Plan.

     12.  OPTIONEES NOT STOCKHOLDERS. Neither the granting of an Option to an
employee nor the deductions from his pay shall constitute such employee a
stockholder of the shares of Common Stock covered by an Option under this Plan
until such shares have been purchased by and issued to him or to an account for
his benefit. Notwithstanding the foregoing, in the event the Company effects a
split of the Common Stock by means of a stock dividend (and the exercise price
of and the number of shares subject to such Option are adjusted as of the date
of the distribution of the dividend rather

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than as of the record date for such dividend), then an optionee who is deemed to
have exercised an Option between the record date and the distribution date for
such stock dividend shall be entitled to receive, on the distribution date, the
stock dividend with respect to the shares of Common Stock.

     13.  RIGHTS NOT TRANSFERABLE. Rights under this Plan are not transferable
by a participating employee other than by will or the laws of descent and
distribution, and are exercisable during the employee's lifetime only by the
employee.

     14.  APPLICATION OF FUNDS. To the extent consistent with applicable law,
all funds received or held by the Company or any Subsidiary under this Plan may
be combined with other corporate funds and may be used for any corporate purpose
and transferred outside the country in which they are deducted from payroll.

     15.  ADJUSTMENT IN CASE OF CHANGES AFFECTING COMMON STOCK. In the event of
a subdivision of outstanding shares of Common Stock, or the payment of a
dividend in Common Stock, the number of shares approved for this Plan, and the
share limitation set forth in Section 9, shall be increased proportionately, and
such other adjustment shall be made as may be deemed equitable by the Board or
the Committee. In the event of any other change affecting the Common Stock, such
adjustment shall be made as may be deemed equitable by the Board or the
Committee to give proper effect to such event.

     16.  MERGER. If the Company shall at any time merge or consolidate with
another corporation and the holders of the capital stock of the Company
immediately prior to such merger or consolidation continue to hold at least 80%
by voting power of the capital stock of the surviving corporation ("Continuity
of Control"), the holder of each Option then outstanding will thereafter be
entitled to receive at the next Exercise Date upon the exercise of such Option
for each share as to which such Option shall be exercised the securities or
property which a holder of one share of the Common Stock was entitled to upon
and at the time of such merger or consolidation, and the Board or the Committee
shall take such steps in connection with such merger or consolidation as the
Board or the Committee shall deem necessary to assure that the provisions of
Section 15 shall thereafter be applicable, as nearly as reasonably may be, in
relation to the said securities or property as to which such holder of such
Option might thereafter be entitled to receive thereunder.

     In the event of a merger or consolidation of the Company with or into
another corporation which does not involve Continuity of Control, or of a sale
of all or substantially all of the assets of the Company while unexercised
Options remain outstanding under the Plan, all outstanding Options shall be
cancelled by the Board or the Committee as of the effective date of any such
transaction, provided that notice of such cancellation shall be given to each
holder of an Option, and each holder of an Option shall have the right to
exercise such Option in full based on payroll deductions then credited to his
account as of a date determined by the Board or the Committee, which date shall
not be less than ten (10) days preceding the effective date of such transaction.

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     17.  AMENDMENT OF THE PLAN. The Board may at any time, and from time to
time, amend this Plan in any respect.

     18.  INSUFFICIENT SHARES. In the event that the total number of shares of
Common Stock specified in elections to be purchased under any Offering plus the
number of shares purchased under previous Offerings under this Plan exceeds the
maximum number of shares issuable under this Plan, the Board or the Committee
will allot the shares then available on a pro rata basis.

     19.  TERMINATION OF THE PLAN. This Plan may be terminated at any time by
the Board. Upon termination of this Plan all amounts in the accounts of
participating employees shall be promptly refunded in local currency or at the
discretion of the Committee or the Board there may be Repayment in Euros.

     20.  GOVERNMENTAL REGULATIONS. The Company's obligation to sell and deliver
Common Stock under this Plan is subject to listing on a U.S. national stock
exchange or quotation on the Nasdaq National Market and the approval of all
applicable governmental authorities required in connection with the
authorization, issuance or sale of such stock.

     21.  GOVERNING LAW. The Plan shall be governed by Massachusetts law except
to the extent that such law is preempted by U.S. federal law or other applicable
law.

     22.  ISSUANCE OF SHARES. Shares may be issued upon exercise of an Option
from authorized but unissued Common Stock, from shares held in the treasury of
the Company, or from any other proper source.

     23.  NOTIFICATION UPON SALE OF SHARES. Each employee agrees, by entering
the Plan, to promptly give the Company notice of any disposition of shares
purchased under the Plan.

     24.  EFFECTIVE DATE. The Plan shall take effect on March 1, 2000.

                                    Approved by the Board of Directors

                                    on February 18, 2000

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                                                                  EXHIBIT 10.1.E

                        AMENDMENT TO EMPLOYMENT AGREEMENT

         This AMENDMENT TO EMPLOYMENT AGREEMENT (the "Amendment") amends that
certain EMPLOYMENT AGREEMENT by and between CLINTRIALS RESEARCH INC., a Delaware
corporation ("Company"), and JERRY MITCHELL ("Executive") dated as of January
30, 1998 (the "Employment Agreement") and is entered into between Company and
Executive this ____ day of _____________, 2000.

         WHEREAS, the parties wish to amend the Employment Agreement as set
forth below;

         IT IS, ACCORDINGLY, AGREED AS FOLLOWS:

         1. Section 4(c) of the Employment Agreement is amended by adding the
following to the end of the paragraph:

                           Notwithstanding the foregoing, the Company Stock
                           Option and any other Company stock options Executive
                           may hold shall vest fully upon a Change of Control
                           (as such term is defined in Section 8(c) hereof) and
                           shall remain exercisable for the remainder of the
                           stated term of such stock option(s), regardless of
                           whether the Executive continues to be employed by the
                           Company.

         2. The portion of the first paragraph of Section 7(c) of the Employment
Agreement labeled "(i)" is amended to read in its entirety as follows:

                  (i)      one and one-half (1 1/2) times the Executive's
                           highest Base Salary during the 12-month period prior
                           to his termination of employment and

         3. Section 7(c)(C)(x) of the Employment Agreement is amended to read in
its entirety as follows:

                  (x) the end of the 18-month period following his termination
         of employment; and

         4. Section 8(a) of the Employment Agreement is amended by adding the
following to the end of the paragraph:

                           In addition, if Executive is terminated as a result
                  of a Change of Control, Executive shall be entitled to the
                  amounts and benefits he

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                  would receive for a termination without Cause under Section
                  7(c). Termination shall be deemed to be a result of a Change
                  of Control (i) if such termination occurs within twelve (12)
                  months following the Change of Control; or (ii) if any change
                  in the Executive's title, reporting relationship,
                  responsibilities or authority as in effect immediately prior
                  to any Change of Control is made within twelve (12) months of
                  such Change of Control and which adversely affects to a
                  material degree his role in the management of the Company; or
                  (iii) if any reduction in the Executive's salary paid to him
                  by the Company as in effect immediately prior to any Change of
                  Control or, if such salary has been subsequently increased at
                  any time or from time to time; any reduction in such increased
                  salary; or (iv) if any termination of the Executive's employee
                  benefit programs, including, but not limited to, any stock
                  option plan, investment plan, savings plan, incentive
                  compensation plan or life insurance, medical plans or
                  disability plans provided by the Company to the Executive and
                  in which the Executive is participating or under which the
                  Company is covered, all as in effect immediately prior to any
                  Change of Control; or (v) if there is any requirement by the
                  Company that the Executive's position and principal office be
                  based and located more than twenty (20) miles outside the
                  boundaries of the principal office of the Executive
                  immediately prior to the Change of Control; or (vi) if any
                  failure or refusal of the Company to renew this Employment
                  Agreement under Section 3 after any Change of Control shall
                  have occurred.

         5. In all other respects the Employment Agreement is hereby ratified
and affirmed.

                                       CLINTRIALS RESEARCH INC.

                                       By:
                                           -------------------------------------
                                       Title:
                                             -----------------------------------

                                       EXECUTIVE

                                       -----------------------------------------
                                       JERRY MITCHELL

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